Experts slam economics of seabed intake for giant US desalination project

A 250 Ml/d seawater desalination (SWRO) plant planned for Huntington Beach, California using sub seafloor intake pipes was “not economically viable at the Huntington Beach location within a reasonable time frame” according to a recent expert report. The findings could jeopardise the Huntingdon project because sub seafloor technology was pivotal to regulatory approval.

The Independent Scientific Technical Advisory Panel, convened by the California Coastal Commission and the plant developer, Poseidon Resources, found that two construction options for a seafloor infiltration gallery (SIG) were viable technically. But in its report it concluded that a SIG was “not economically viable at the Huntington Beach location within a reasonable time frame due to high capital costs and only modest reduction in annual operating costs.”

The advisory panel said the economic viability of the technology at Huntingdon was “highly uncertain” and that it was “unlikely that the unit price for produced water from a SWRO plant with the SIG intake technology would find a buyer under current and likely future estimates of alternative waters sources through 2033.”

The panel calculated that Poseidon’s favoured open ocean intake would have a unit cost 40-50% less than the sub seabed technology. It proposed that Orange County Water District “might be willing to pay these water costs in 2018,”

A sub seafloor approach was favoured on environmental grounds by the coastal commission whose approval is required before construction can begin so the findings.

In 2013 the coastal commission concurred with environmentalists who, on the grounds of danger to marine life objected to an open-ocean intake system. Poseidon withdrew its coastal permit application that year after the commission said its approval for the project would require Poseidon to use subsurface pipes. Subsequently the commission and Poseidon jointly selected the advisory panel which has considered the economic and environmental feasibility of sub seabed intakes.